Abstract: A method and apparatus for measuring the gamma radiation levels of drilling mud expelled from an oil and gas bore hole to determine the composition of the earth at the bottom of the bore hole and, when used in conjunction with a Measurement While Drilling gamma radiation detector, to determine the time and location of bore hole cavings. A first gamma radiation detector measures the gamma radiation level of the drilling mud with the bore hole entrained material, and a second gamma radiation detector measures the gamma radiation of the drilling mud without the entrained material. The difference between the two measurements is lagged to the time between the detectors and the bore hole bottom.

Abstract: The present invention is a gas sampling device. A gas sampling tube and pump withdraw gas which evolves into the atmosphere as the drilling fluid in the annular space exits the wall bore. Drilling fluid and debris which may be entrained in the gas sample are separated by gravity settling in a separation device. A purge line may be used to agitate drilling mud and force gas toward the gas sampling tube.